The present invention relates generally to fiber optic switches, and, more particularly, concerns a device and method for direct switching of optical signals between input and output optical fibers with minimal optical losses.
Due to advantages over conventional electrical transmission mediums such as increased bandwidth and improved signal quality, the use of fiber optics in communications networks has become commonplace. However, as with electrical signals transmitted over wires which need to be switched between various wires in order for the signals to reach their intended destinations, optical signals similarly need to be switched between different optical fibers at appropriate junctions so that the optical signals reach their intended destinations.
One method of switching an optical signal between fibers is to convert the optical signal to an electrical signal, employ conventional electronic switching components to switch the electrical signal, and then re-convert the electrical signal to an optical signal. An alternative approach is to employ direct optical switching wherein the optical signal is directed between fibers. The latter approach has distinct theoretical advantages, including an increase in switching speed and a reduction in signal degradation, because it eliminates the optical-to-electrical and electrical-to-optical conversions.
When implementing direct optical switching, it is desirable to have the capability to switch an optical signal from any one of a number of optical fibers entering a junction (input fibers) to any one of a number of optical fibers exiting a junction (output fibers). Several ways of achieving this have been previously proposed. One way is to bend the ends of the selected input and desired output fibers such that the two fibers point at one another (directly or via a folded optical pathway) providing a direct optical pathway for the optical signal between the fibers. The use of fixed reflectors, such as mirrors, in conjunction with bending the fiber ends has also been previously proposed. The fiber ends are not bent to point at one another, but rather are directed at one or more reflectors so that an optical signal from the input fiber is reflected to the output fiber.
One object of the present invention is to provide for direct switching of optical signals between optical fibers.
The present inventor has recognized that to achieve efficient and accurate switching of the optical signal when implementing direct optical switching, it is desirable that the optical signal be directed from the input fiber such that it enters the output fiber along an optical pathway that is in substantial alignment with the output fiber. Accordingly, another object of the present invention is to provide for direct switching of optical signals between input and output optical fibers wherein the optical signal enters the output fiber along an optical pathway that is in substantial alignment with the output fiber.
The present inventor has also recognized that forming the optical signal into a focused beam, as opposed to a collimated or other diverging signal, before directing it to the output fiber with one or more reflectors is desirable in order to reduce loss of the optical signal and improve effectiveness of the switching operation. Accordingly, a further object of the present invention is to provide for direct switching of optical signals between input and output optical fibers wherein the optical signal emitted from the input fiber is formed into a focused beam before directing it to the output fiber with one or more reflectors.
These and other objectives and advantages of the present invention are achieved by various aspects of the present invention. According to one aspect of the invention, first and second reflectors, for example mirrors, are provided wherein the first reflector is associated with the input fiber and the second reflector is associated with the output fiber. The first reflector receives the optical signal from the input fiber and is oriented so that it reflects the optical signal in a manner such that it reaches the second reflector, either directly from the first reflector or by further reflection off of other reflectors. The second reflector receives the reflected optical signal and is oriented so that the optical signal is further reflected to the output fiber along an optical pathway having an axis that is in substantial alignment with the axis of the output fiber.
In another aspect of the present invention, the first reflector does not reflect the optical signal directly to the second reflector. Rather, the optical signal from the input fiber is reflected by the first reflector to a third reflector which then reflects the optical signal to the second reflector. Further reflectors may be employed. For example, in one embodiment, the first reflector reflects the optical signal to a third reflector, which reflects the optical signal to a fourth reflector, which, in turn, reflects the optical signal to the second reflector.
In yet another aspect of the present invention, multiple reflectors are arranged into first and second arrays of reflectors, with each reflector of the first array being associated with a separate one of a plurality of input fibers and each reflector of the second array being associated with a separate one of a plurality of output fibers. The reflectors of the first and second arrays are positionable in a plurality of orientations relative to a reference orientation. For example, the reflectors of the first and second arrays may be rotatable about at least one axis of rotation to allow for positioning of the reflectors in a plurality of orientations. An optical signal may be switched between any selected one of the input fibers and any selected one of the output fibers by positioning the reflector of the first array associated with the selected input fiber in an orientation such that the optical signal is reflected, either directly or by additional reflectors, to the reflector of the second array associated with the desired output fiber. Preferably, the reflector of the second array associated with the selected output fiber is correspondingly positioned in an orientation such that the optical signal incident thereon is reflected along an optical pathway having an axis substantially aligned with the desired output fiber.
A still further aspect of the present invention involves a beam-forming unit associated with an input fiber and an associated beam-directing system for directing the beam on an optical path towards a selected output fiber. The beam forming unit associated with the input fiber receives the optical signal emitted from the end of the selected input fiber and forms it into a focused beam, as opposed to a collimated or other diverging signal. The focused beam optical signal is then directed by the beam-directing system to the selected output fiber. The output fiber is preferably associated with a lens arranged in a focused configuration relative to the beam-forming unit and the output fiber. It will thus be appreciated that a symmetric optical pathway is defined whereby an optical signal from the input fiber is made to enter the end of the output fiber. This arrangement allows for efficient bi-directional communication between the input and output fibers (the xe2x80x9cinputxe2x80x9d and xe2x80x9coutputxe2x80x9d labels being merely a convenience).
One more aspect of the present invention involves a method for switching optical signals between an input fiber and an output fiber. The method involves forming the optical signal into a focused beam, directing the beam towards the output fiber along an optical pathway that is, prior to the beam reaching the output fiber, substantially aligned with the output fiber, and receiving the optical signal on the end of the output fiber. A symmetrical focused beam forming unit comprised of a first focused beam forming unit and a second, substantially identical focused beam forming unit may be employed in the forming and receiving steps to enhance optical signal transmission. The step of directing may be accomplished with two active reflectors each associated with one fiber.
These and other aspects and advantages of the present invention will be apparent upon review of the following detailed description when taken in conjunction with the accompanying figures.